1. Field of the Invention
This invention relates to railcar-moving vehicles that are adaptable both for moving railcars along railroad track and for pulling trailers on roadways. More particularly, the present invention relates to a railcar-moving vehicle that also functions as a rubber-tired highway vehicle, and which incorporates an improved load-shifting device for transferring a portion of the railcar load to the drive wheels of the vehicle in order to improve traction.
2. State of the Art
In the railroad industry, maintenance of way is a critical activity and a major expense. Frequently, when maintenance is needed at a particular location along the right-of-way and heavy equipment or materials are required, a work train and crew are sent to that location to perform the needed repairs. For example, a work train may carry a load of railroad ties and short sections of rail for repairing track, and may include some pieces of heavy equipment for unloading and installing these items. Often, a work train consists of a locomotive pulling a single work car, and the maintenance work can be performed by one or two workers.
However, this approach can be very cost inefficient. Because maintenance of way crews and locomotive crews are differently trained and unable to perform each other""s duties, the work train will frequently employ a crew much larger than actually needed at any given time. Obviously, this is costly. Furthermore, the use of a typical locomotivexe2x80x94which may cost in excess of a million dollarsxe2x80x94to transport a single car and a few workers is extremely cost inefficient. For these reasons, it would be desirable to have a railcar-moving vehicle that can pull one or a few railcars along the railroad track at mainline speeds, but that is not a conventional locomotive, and thus is not as costly as a locomotive, nor requires a full locomotive crew. With such a vehicle a work crew could transport themselves to the work site with their materials and equipment, and perform the work with far less expense for labor and equipment.
Additionally, it would be desirable to have such a railcar-moving vehicle that is operable both on rails and on roadways. Such a vehicle would be valuable for maintenance of way crews by allowing a work crew to transport themselves and their equipment by highway to a rail siding, where the crew simply transfers their materials and equipment to a waiting railcar, and uses the semi tractor on the rails to pull the work railcar to the work site.
This sort of vehicle would have additional uses, as well. For example, many railroad customers have a need to move railcars and highway trailers around a rail yard or industrial site. However, except for the largest industries, the cost to purchase and maintain a conventional switching locomotive is prohibitive or economically unwarranted. Thus, lightweight multipurpose railcar-moving vehicles have been developed and used to perform many functions normally assigned to switching locomotives, but which may also be used off the track. Such modified or hybrid vehicles are more economical for many industries because of their relatively low cost and high versatility. They allow smaller industries to take advantage of the efficiency and economy of rail transport for heavy freight where otherwise they would not be able to do so.
However, conventional lightweight railcar-moving vehicles are still relatively highly specialized, limited production vehicles. The cost per horsepower of these vehicles is significantly higher than the cost of a conventional semi tractor, for example, which enjoys the cost advantages of greater mass production. Additionally, conventional railcar-moving vehicles are not designed or configured to operate on public highways as long or short haul trucks, but are confined to an industrial site or switching yard. Many of them do not have the functional and safety equipment required to be street legal, and are designed for low speed operation only, being unable to travel at speeds beyond 15 to 20 miles per hour. Moreover, they cannot operate at top speed for extended periods of time without overheating their hydraulic systems. It would thus be desirable to have a railcar-moving vehicle which is constructed from a mass produced vehicle, such as a semi tractor, so as to reduce the acquisition cost of these vehicles. It would also be desirable to have a railcar-moving vehicle which is capable of extended operation at high speeds and can be conveniently and legally used for either long or short haul transport of freight on public highways.
Because a loaded railcar may be much heavier than one of these lightweight traction vehicles, various methods have been developed to transfer a portion of the weight of the railcar to the traction vehicle. These methods typically involve some sort of hydraulic system which applies a vertical force to the drawbar of an attached railcar, so as to transfer a portion of the weight of the railcar to the traction vehicle. This transfer helps provide traction to the railcar-moving vehicle to allow it to move the railcar without slippage of the drive wheels on the track. However, the devices now known typically involve a coupler extending from one end of the vehicle which lifts the load outboard of the drive and support axles of the vehicle. The load-shifting mechanism does not provide any horizontal movement so as to move the bearing point of the load more directly over the wheels of the traction vehicle. Those knowledgeable in mechanical design will understand that placing the load closer to the nearest supporting axle or between a pair of supporting axles will distribute the load more evenly, and in the case of multiple drive axles, will thereby provide more traction. Additionally, placing the load closer to the nearest supporting axle or between the axles will reduce the moment which tends to lift the end of the vehicle opposite the load. It would thus be desirable to have a railcar-moving vehicle which both lifts and forwardly advances a coupled railcar so as to transfer a portion of the load of the railcar to the vehicle and to move the point of bearing of the load closer to the nearest supporting axle, or between supporting axles.
The invention advantageously provides railcar-moving vehicle that is capable of extended operation at highway speeds both on and off rails. The vehicle comprises a modified semi tractor with retractable railroad wheels and an air bag suspension system. A load-shifting device is pivotally disposed rearwardly on the vehicle frame, to which the rearward rail wheels are attached. The load-shifting device includes a lifting coupler configured to couple to a coupler of a railcar. A coupler airbag is disposed between the rearward rail wheels and the lifting coupler, and is configured to inflate with compressed air concurrently with the air bag suspension system, so as to apply upward force upon the coupler of the railcar and downward force on the drive wheels, which directly contact the rails, so as to transfer a portion of the weight of the railcar to the drive wheels of the railcar-moving vehicle.
Other objects and features of the present invention will be apparent to those skilled in the art, based on the following description, taken in combination with the accompanying drawings.